Polyester shrink film have become important in the packaging industry, primarily because they can be disposed of by incineration, or recovered and recycled from labels on poly(ethylene terephthalate) (PET) bottles. Shrink films have been improved in the trade by composition modifications and certain processing manipulations.
However, shrink films are still ineffective for practical purposes. Especially when used on such items as rectangular bottles, wrinkling and film distortion are very obvious. The development of a shrinkable polyester film having improved shrinking properties is desired. We have unexpectedly found that an improved polyester shrink film suitable for practical use can be produced using certain copolyester modifications.
Shrinkable copolyester films disclosed in U.S. Pat. No. 5,070,180 do not use cycloaliphatic acids, such as 1,4-; 1,2-; and 1,3-cyclohexanedicarboxylic acid and their cis/trans isomer mixtures. Two other U.S. Pat. Nos. 4,766,033 and 4,020,141 discuss attempts to prepare copolyester shrink film. However, none of these patents address the copolyester compositions disclosed in this invention. We have discovered that the use of the cycloaliphatic carboxylic acids and their esters impart a significant degree of improved color, thermal stability and weatherability.